Method and system for key insertion for stored encrypted content

Abstract

An encrypted content transport stream is received by a viewer's device and recorded for subsequent playback. During recording, keys in headers of packets of the stream are stripped and placed in sequence in a table. Also, the table indicates changes in key indicating bits. When it is desired to play the content, start-of-frame indicator bits such as PUSI and/or RAI bits are used to access the table of keys to retrieve the keys necessary to decrypt the transport stream packets sought to be played.

1. A method for playing content embodied in a data stream, at least portions of the content being received in an encrypted form, comprising:
 establishing at least one table of keys received in the data stream; 
 for at least one packet of the data stream, decrypting the packet and playing the packet at least in part by: 
 accessing the table using a processor to identify at least one key associated with the packet; and 
 using the key to decrypt the content, wherein the keys are contained in packets in the data stream, and 
 stripping the keys from packets and placing the keys in the table. 
 
   
   
     2. The method of  claim 1 , further comprising displaying the content on an output device. 
   
   
     3. The method of  claim 1 , wherein the keys are encrypted, and the keys are decrypted after the act of accessing the table and prior to using the keys to decrypt the content. 
   
   
     4. The method of  claim 1 , wherein the data stream is composed of packets, each packet being one hundred eighty eight (188) bytes in length. 
   
   
     5. The method of  claim 1 , wherein the table includes encryption-indicating bits received in headers of packets of the data stream. 
   
   
     6. The method of  claim 5 , comprising: receiving a user-initiated trick mode jump from a first video packet to a second video packet; changing the polarity of at least some encryption-indicating bits following the second packet if the encryption-indicating bits associated with the first packet indicate the same key polarity as the encryption-indicating bits associated with the second packet. 
   
   
     7. The method of  claim 1 , wherein the table is accessed at least in part based on at least one start-of-frame indicating bit associated with the packet sought to be decrypted, to facilitate trick mode playback. 
   
   
     8. A playback device, comprising: at least one content store configured for holding encrypted content, the content including a data stream of content data packets, at least one packet containing at least one key; and at least one processor accessing the store and programmed with logic to: arrange the key in a key table; and link keys in the table with key changes in the data stream, to facilitate subsequent decryption and playback of the content. 
   
   
     9. The device of  claim 8 , wherein the header contains at least one encryption-indicating bit, and the processor: establishes at least one index cable indicating changes in encryption-indicating bits in the data stream, entries in the index table being correlated to keys in the table; decrypts the packet and plays the packet at least in part by: accessing the index table to identify at least one key associated with the packet; and using the at least one key to decrypt the content. 
   
   
     10. The device of  claim 9 , comprising: means for receiving a user-initiated trick mode jump from a first video packet to a second video packet; and means for changing the polarity of at least some encryption-indicating bits following the second packet if the encryption-indicating bits associated with the first packet indicate the same key polarity as the encryption-indicating bits associated with the second packet. 
   
   
     11. The device of  claim 9 , wherein the encryption-indicating bits are in headers of packets of the data stream. 
   
   
     12. The device of  claim 8 , wherein the processor displays the content on an output device. 
   
   
     13. The device of  claim 8 , wherein the keys are contained in packets in the data stream, and the processor strips the keys from packets. 
   
   
     14. The device of  claim 8 , wherein the keys are encrypted, and the processor decrypts the keys after accessing the table and prior to using the keys to decrypt the content. 
   
   
     15. The device of  claim 8 , wherein the data stream is composed of packets, each packet being one hundred eighty eight (188) bytes in length. 
   
   
     16. The device of  claim 8 , wherein the table is accessed at least in part based on at least one start-of-frame indicating bit associated with the packet sought to be decrypted, to facilitate trick mode playback. 
   
   
     17. A system for providing to viewers trick playback of encrypted content, comprising: and at least one content provider transmitting at least one encrypted data stream; at least one viewer device receiving the data stream, stripping encryption keys therefrom, and linking the keys to corresponding packets of the data stream, such that subsequent decryption and trick mode playback is facilitated. 
   
   
     18. The system of  claim 17 , wherein the data stream includes key packets containing keys, the keys being arranged in a key table subsequent to being stripped from the packets. 
   
   
     19. The system of  claim 18 , wherein at least one header contains at least one encryption-indicating bit, and the viewer device includes means for indicating changes in encryption-indicating bits in the table. 
   
   
     20. The system of  claim 19 , wherein the device decrypts the packet and plays the packet by accessing the table to identify at least one key associated with the packet, decrypting the key, and using the key to decrypt the content. 
   
   
     21. The system of  claim 19 , wherein the data stream is composed of packets, each packet being one hundred eighty eight (188) bytes in length. 
   
   
     22. The system of  claim 19 , wherein the table is accessed at least in part based .on at least one start-of-frame indicating bit associated with the packet sought to be decrypted. 
   
   
     23. A computer program device, comprising: means for establishing at least one table of keys received in a data stream: means for linking the keys to changes in encryption-indicating bits in the data stream; means for, for at least one packet of the data stream, decrypting the packet and playing the packet at least in part by: accessing the table to identify at least one key associated with the packet; and using the at least one key to decrypt the content. 
   
   
     24. The computer program device of  claim 23 , further comprising means for displaying the content on an output device. 
   
   
     25. The computer program device of  claim 23 , wherein the keys are contained in packets in the data stream, and the computer program device comprises means for stripping the keys from packets and placing the keys in the table. 
   
   
     26. The computer program device of  claim 25 , wherein the keys are encrypted, and the device includes means for decrypting the keys. 
   
   
     27. The computer program device of  claim 25 , comprising means for accessing the table at least in part based on at least one start-of-frame indicating bit associated with the packet sought to be decrypted. 
   
   
     28. A method for playing content embodied in a data stream, at least portions of the content being received in an encrypted form, comprising:
 receiving a data stream including content and at least one key, where a key corresponds to at least part of the content in said data stream; 
 retrieving at least one key from said data stream using a processor; 
 establishing a table of keys using at least one retrieved key; and playing at least a part of the content from said data stream by: 
 identifying a key associated with the part of the content by accessing said table of keys, and decrypting the part of the content using the identified key.